Deletion of the Wilms’ Tumor Suppressor Gene in the Cardiac Troponin-T Lineage Reveals Novel Functions of WT1 in Heart Development

Abstract

Expression of Wilms’ tumor suppressor transcription factor (WT1) in the embryonic epicardium is essential for cardiac development, but its myocardial expression is little known. We have found that WT1 is expressed at low levels in 20–25% of the embryonic cardiomyocytes. Conditional ablation of WT1 using a cardiac troponin T driver (Tnnt2Cre) caused abnormal sinus venosus and atrium development, lack of pectinate muscles, thin ventricular myocardium and, in some cases, interventricular septum and cardiac wall defects, ventricular diverticula and aneurisms. Coronary development was normal and there was not embryonic lethality, although survival of adult mutant mice was reduced probably due to perinatal mortality. Adult mutant mice showed electrocardiographic anomalies, including increased RR and QRS intervals, and decreased PR intervals. RNASeq analysis identified differential expression of 137 genes in the E13.5 mutant heart as compared to controls. GO functional enrichment analysis suggested that both calcium ion regulation and modulation of potassium channels are deeply altered in the mutant myocardium. In summary, together with its essential function in the embryonic epicardium, myocardial WT1 expression is also required for normal cardiac development.

"Sudden Cardiac Death in Young Adults: Population Aspects in Bihor County, Romania"

“…WT 1 gene is normally expressed in epicardium, playing an important role in heart developing, in time of embryogenesis. At low levels, up to 25%, WT1 gene may be expressed also in embryonic cardiomyocytes [17]. Studies show [17] that WT1 overexpression, in adults, on a distress myocardium, is present in angiogenesis process in the suffering endothelial cells at the border zone of hypoxia.…”

“…At low levels, up to 25%, WT1 gene may be expressed also in embryonic cardiomyocytes [17]. Studies show [17] that WT1 overexpression, in adults, on a distress myocardium, is present in angiogenesis process in the suffering endothelial cells at the border zone of hypoxia. In young adults, the overexpression of WT1 gene may help the forensic doctor to find out the cause of death in the early hours.…”

Regulation of Epicardial Cell Fate during Cardiac Development and Disease: An Overview

“…Although the contribution of EPDCs to endothelial cell and cardiomyocyte lineages remains under debate, recent reports have revealed that a minor fraction of coronary endothelium cells are derived from the epicardial GATA5 and myocardial cTnT lineages [ 4 ]. Furthermore, a small population of embryonic cardiomyocytes that expresses WT1 at low levels has recently been described; these WT1 lineage-derived cardiomyocytes are similar to a progenitor population named juxta-cardiac field (JCF), identified by single-cell RNA sequencing of mouse embryonic hearts [ 5 , 54 ]. Nevertheless, many discrepancies observed in the differentiation potential of EPDCs may be due to the fact that most of the promoters used in epicardial lineage-tracing models are not uniformly expressed and have a restrictive temporal expression pattern in the epicardium [ 5 , 55 ].…”

“…Furthermore, a small population of embryonic cardiomyocytes that expresses WT1 at low levels has recently been described; these WT1 lineage-derived cardiomyocytes are similar to a progenitor population named juxta-cardiac field (JCF), identified by single-cell RNA sequencing of mouse embryonic hearts [ 5 , 54 ]. Nevertheless, many discrepancies observed in the differentiation potential of EPDCs may be due to the fact that most of the promoters used in epicardial lineage-tracing models are not uniformly expressed and have a restrictive temporal expression pattern in the epicardium [ 5 , 55 ]. In this regard, a comparative study performed by Carmona et al in four different epicardial lineage-tracing systems (WT1 Cre , GATA5 Cre , G2-GATA4 enhancer, and cTnT Cre ) demonstrated that, although WT1 Cre driver seems useful in tracing the cell fate of EPDCs before E13.5, the interpretation of some WT1-lineage traced analyses can be difficult at later embryonic stages considering that later de novo expression may increase the proportion of Wt1-lineage cells [ 4 ].…”

“…During this process, the epicardium constitutes a population of multipotent progenitors that, after undergoing an epithelial-to-mesenchymal transition (EMT), migrate into the myocardium as epicardium-derived cells (EPDCs) [ 1 ]. EPDCs give rise to various cardiac cell types, including coronary vascular smooth muscle cells, cardiac fibroblasts, endothelial cells, and presumably a subpopulation of cardiomyocytes, thus contributing to complete heart formation [ 2 , 3 , 4 , 5 ]. However, it remains unclear as to how different cell types emerge from EPDCs and the molecular mechanisms underlying epicardial-derived cell fate during heart development.…”